Skip to main content

Full text of "Use of mines in trench warfare : from the French school of St. Cyr"

See other formats


OCL( - ?"*- 





(From the French School of St. Cyr) 


JULY, 1917 




Document No. 635. 
Office of The Adjutant General. 


WASHINGTON, July 23, 19 11. 

The following notes on Use of Mines in Trench Warfare are 
published for the information of all concerned. 
[062.1, A. G. 0.] 



Major General, Acting Chief of Staff, 


The Adjutant General. 


Washington, June 19, 1917. 
To all officers of the Army: 

You are advised that this and all subsequent documents of a 
similar character which may be furnished to you from this 
office are to be regarded as strictly confidential. They are to be 
kept at all times in your personal possession, and are not to be 
copied, nor are any parts of their contents to be communicated 
either directly or indirectly to the press, nor to any person not 
in the military or naval service of the United States. In 
Europe these documents are not to be carried into the front-line 
trenches, nor farther to the front than the usual post of the 
officers to whom issued. 

Strict compliance with this injunction is enjoined upon every 
officer into whose hands any of these confidential documents 
may come. 



The Adjutant General. 



Use of mines 5 

Specially menaced points 5 

Surface observations 5 

Indications revealing enemy galleries 6 

Listening for underground noise 6 

Position of listening posts 6 

Hours and precautions 7 

What is heard 7 

Distance at which noise can be heard 7 

Direction from which noise comes 8 

Useful information on mines 8 

Defensive systems 8 

Interval between galleries 8 

Start, depth, and progress of work 9 

Barrage trench for miners 9 

Camouflet 9 

Offensive galleries 10 

Superimposed galleries 10 

Mine chamber 11 

Launching an attack 11 

Craters 11 

Craters to be occupied 11 

Craters that the enemy occupies 12 

Craters not occupied 12 

Diagrams 9, 10, 12, 13 

4387 1 7 4 


[From the French St. Cyr School.] 

(Secret and Confidential. For Official Use Only. Not to be Taken into 
First-Line Trenches.) 


In sectors where the distance between the two lines is below 
150 meters, mine warfare must be used. When the trenches are 
farther apart, underground warfare is seldom employed. In 
special cases, however, when there are strong ventilators and the 
line is stable enough to permit of it, advance may be made 


The most vulnerable points evidently are the following- : The 
outposts in advance of the line, machine-gun positions approxi- 
mately located by the enemy, and the junction points of the 
communicating trenches with the first line. 


Underground activity, either offensive or defensive, is first 
observed from those points in our lines nearest to it. All 
enemy trenches facing a salient of our lines will be the object 
of particular attention and closest daily observation. This obser- 
vation of the first-line trenches should disclose the presence of 
enemy underground works and their approximate location. 

One of the difficult questions in mining is the removal of the 
earth. Expert miners sometimes remove the earth as far as 100 
to 200 meters from the entrance to the gallery. They throw it 
on old ruined shelters, in shell holes, on the reverse of the 
trenches. But these precautions are not always rigidly observed. 
When the noncommissioned officer is absent, or the enemy bom- 
bards a little strongly, some one in the working party not want- 
ing to work overtime throws several clods of earth on the 




Freshly placed earth coming from underground is white and 
less dull in color than that of the parapets, which have been 
washed by the rain and blackened by explosives. The differ- 
ence in color for the first day or so is striking. In chalk, large 
white spots are seen on the reverse of the German trench, daily 
growing larger. Without doubt they are working near by, and 
should be watched. 

A communication trench comes out at a salient, and runs back 
from 150 to 200 meters. Patches of chalk, freshly moved and 
increasing daily, are observed. These are indications of un- 
derground work starting from the salient. 

Four or five meters of enemy trench without loopholes, but 
with loopholes close together to the left and right, may mark a 
gallery entrance. 

A miner's working relief reaches the gallery, each man carry- 
ing a piece of the frame or a lining plank over his shoulder, the 
ends of which can be seen over the parapet or through the 
loopholes. These are indications of a gallery position, espe- 
cially if the men all move in the same direction and are lost to 
view at the same place. 

From a raised point on the second or third line we see, with 
field glasses, an abnormal accumulation of sandbags in a well- 
known area. These sacks may indicate an underground gal- 

Patrols sent out in front of the enemy trenches sometimes 
bring back valuable information. They may hear the rumble 
of ventilators, the noise of a truck moving on the rails, men 
working near a gallery entrance, etc. 

The enemy fire with heavy calibers on portions of the first 
line. Often the same corner is bombarded. This may indicate 
that the enemy artillery is seeking to facilitate the miner's 
work by overthrowing the entrances to troublesome galleries in 
the trench attacked. 

Listening for underground noise. The observation of hostile 
trenches may give indications which will limit the zone necessary 
to be watched ; but for accurate results we must listen for under- 
ground noises. 

Positions of listening posts. The listening post is placed at 
the head of a gallery, in an angle of a gallery, in a deep dug- 
out, in a niche under the parapet, or on the bottom of the 

trench. The points nearest to the enemy trench are selected 
for the listening posts. Below the outposts there is always a 
niche, allowing a man to place his ear to the. ground (hence the 
name listening posts). 

Hours and precautions. The most favorable hours are morn- 
ing about 4 or 5 o'clock, at 2 p. m., and at midnight. All the 
occupants of that part of the trench must keep still, and all 
work in the trench and the mine must cease for a given time. 

What is heard. The inexperienced ear hears too many things, 
and is easily mistaken in the noises heard. A relief passing in 
the enemy trench or in his own trench at 40 meters sounds 
strangely like the noise of a pick. A man hitting a ground sill 
or striking it with his heel gives the. idea that work is being 
done. The impact of bullets on the parapet at night, when a 
fusillade is uninterrupted, also gives the idea of underground 
work. A man filing a fuse at the foot of his loophole suggests 
the presence, of an enemy revolving borer. A man who snores 
beside the gallery entrance imitates the noise of a ventilator 
and may be mistaken for it. 

However, to even a partially trained ear the noise of the 
pickax is characteristic. It is not a harsh sound, like that of a 
heel striking on chalk ground, nor is it like the shock of bul- 
lets piercing the parapet. It is a low, rhythmic sound, with 
regular cadence. In a gallery the miner works kneeling. When 
he has struck five or six blows with the pickax, he takes a 
breath. He repeats this process about 12 times. He stops two 
or three minutes, and the second miner clears away the earth 
and fills the truck with sacks. The first miner resumes his 
work. It is easy to distinguish this regular cadence peculiar to 
the miner. 

In an infantry company there are always several miners by 
occupation, or several men familiar with engineering. These 
men are selected specially for the listening service. They can 
give accurate information to the officers and noncommissioned 
officers of a sapper company. It is also a good thing for a 
platoon commander to descend into a gallery and train his ear 
by exchanging pickax signals with the miner in the adjoining 

Distance at ^vhich noise can ~be heard. The following indi- 
cations help in determining the distance of underground work : 

Four men work in a gallery. They start the work, then 
stop. The ear is placed against the side of the wall, the other 


ear being covered by the hand. If the work is heard under these 
conditions, it is at a distance of 25 to 30 meters. 

If all noise is avoided, and the work is heard without placing 
the ear against the wall, the distance is 12 to 15 meters. 

If there is talking or working going on, and still the under- 
ground work is heard in spite of it, the distance is 8 to 10 meters. 

At six meters a man can hear all the sounds of the pickax, the 
chalk crumbling, the pieces rolling down on one another, the 
sliding and stacking of cases. These noises sound as if they 
were immediately below. 

At four meters a man can hear talking, the scraping of but- 
tons against the wall, the miner turning around. 

The humming of a ventilator can be heard at 40 meters with- 
out taking precautions to hear it. 

An automatic borer can be heard all through the sector. 

Directions from ichich noise comes. It is easier to deter- 
mine the direction of noise than the distance. There is always 
a chance of making observations in the galleries one on the 
right, the other on the left of the noise. The exact location 
of the enemy underground work can be determined by inter- 

The engineer companies have an apparatus for intensifying 
the sound (strong microphones). They reinforce the sound 
when the apparatus is in the direction of the source of the 
sound. Their greatest defect is that they magnify sound too 
much and too many things are heard. Why hear for a distance 
of 100 meters when the enemy trench is only 40 meters away? 
Everything is heard in a mine gallery. It is difficult to dis- 
tinguish among the many noises that of the enemy miner's pick. 
The ear is amply sufficient. 

The beginner has a tendency to exaggerate the proximity of 
sounds. He thinks he is close to the enemy when he is still 
at a distance, and he takes steps to catch the enemy by ex- 
ploding a camouflet, whose only effect is to retard his own work. 


Defensive system. Two arrangements can be adopted : Fan- 
shaped arrangement (fig. a) or arrangement of independent 
parallel galleries (fig. b). The second arrangement is prefer- 

Interval between galleries. Arrangement 2 being adopted, cal- 
culate the interval between two neighboring galleries in such 


manner as to prevent the enemy working underground. At the 
head of each gallery two elbows of 6 meters, with boring cham- 
bers, are made. A 6-meter boring is made from each chamber. 
At the bottom of the boring a camouflet is placed, effective for 
radius of 6 meters (not more heavily charged or the gallery 
will be demolished). The camouflet of the neighboring gallery 
forms a tangent to the first. The interval between the two 
galleries can not, therefore, be greater than 36 meters. In 
practice we would take 30 meters. 

Start, depth, and progress of work. Start from first line. 
Start at 4 meters, with a slope of 20 per cent to 30 per cent 
down to a depth of 10 meters. Then horizontal. Length to 
gallery and return without ventilation can cover 30 meters. 

Barrage trench for miners. If the enemy passes in spite of 
everything, the explosion should at least have been foreseen. 
The enemy's attack must be limited or stopped, and this is 
always possible after the explosion of the charge, which may 
explode well in advance of our lines and act only as a strong 
means of launching his attack. The barrage trench is estab- 
lished at from 40 to 50 meters in rear of the salient T (fig. 2). 
In front of the parapet T, wire entanglement R, and two ma- 
chine-gun positions M and M 2 are placed. When the enemy's 
explosion is near, only a few men are left to occupy the salient. 
The German explosion does not bury anyone, and when the 
attack is launched it breaks down at the entanglement R. 

Camouflet. The sector commander is warned when the de- 
fense is about to explode a camouflet. About 10 meters on each 
side of the gallery are evacuated as a precaution. The only danger 


is in having several sandbags fall on the sides of the gallery 
entrance. Warn the working party charged with the relief, in 
order that they may not block the passage of men in the first, 
line. Do not fire or make any changes in that part of the 
trench, in order that the enemy may not locate the position. 
Do not fire rockets before a given time. The camouflet some- 
times shakes the ground and dust is visible. Nine times out of 
ten the camouflet is used at night. 

When the. enemy explodes a camouflet, fire a quantity of 
rockets to locate the positions. Fire grenades and throw bombs 
at the presumable position of the gallery. Send several men in 
front of the parapet to listen to what is going on in the enemy 

Offensive galleries. These are intended to pass under the 
adversary's defenses. Depth. Start at first line when it is far 

enough away from the enemy. Start at second line, or at 
special communication trench about 20 meters in the rear of 
the first line, when the enemy trench is too near. (See preced- 
ing.) A depth of 15 to 18 meters should be attained. The 
work is done as in ordinary galleries. 

Superimposed galleries. This procedure gives splendid re- 
sults in deceiving the enemy, who thinks he is protecting him- 
self. The defensive gallery starts at the first line and the 
offensive gallery starts in rear of it. Both galleries are on the 
same vertical plane, the second being more advanced in the 
direction of the enemy than the first. An enemy listener easily 
confuses one with the other, and the offensive gallery passes 
under him. (See figure.) Distances D and D 1 are the same. 
The miner, M, confuses the two sounds, and the offensive 
gallery passes under him. 


Mine chambers. They are of special interest to the Engineer 
Corps from a technical point of view. The best hours for 
exploding them are 4 a. m. and 7 p. m. When an attack is 
launched at a great distance, or when there is to be no attack, 
the explosion is preceded by several minutes of noise in the 
trenches. We commence firing and show several bayonets over 
the parapet. The enemy believes an attack is coming, comes 
out of his shelter, and mans his trenches. After the explosion 
we fire on the mine crater for four hours with artillery, grenades, 
and bombs. This fire should cover all the area exploded by the 
mine chamber and should prevent any help to the wounded or 

Launching an attack by means of mining. The mine is an 
irresistible means of launching an attack. In a mined sector 
the best troops completely lose their bearings for several seconds 
after an explosion. These several seconds prevent the machine 
gun from firing, and the assailant gains a foothold in the first 
line and often in the second. 

A mine attack should be prepared in the following manner : 

Several days beforehand the attacking troops are sent to the 
rest camp. The plan of the junipiug-off trenches, the trenches 
to be attacked, the ground trace of the crater, and the zone of 
the searchlights are drawn on the ground with chalk. Each 
attacking fraction is placed in position, with the materiel to be 
carried. Each fraction's line of advance is marked out in 
chalk, as well as the section of the enemy's trench to be occupied 
and the position of the barrage. Every detail is studied thor- 
oughly, and the exercise repeated a dozen times. The attack 
is then carried out as planned. 

Craters. The question of the occupation of craters must be 
decided by an authority higher than the platoon commander. 
In certain cases it is well to occupy them ; in others, inadvisable-'. 
We will discuss only the practical work to be done in each case. 

Craters to be occupied. Crown the rim on the enemy side 
with a continuous trench, joined to the lines by (at least) two 
communicating trenches. Run out galleries in three directions, 
first for protection and later for use in the attack. Construct 
bombproofs on the half cone on the enemy side. 

A crater is a position advantageous for the construction of 
auxiliary defenses, for the removal of earth from the galleries, 
for massing troops for an attack, and for flanking the lines. 


Craters that the enemy occupies. They should be hampered 
with bombs and grenades. We should head off the enemy by 
means of two well-placed mine chambers, which are always 
possible to fire rapidly when the scheme of defense is by inde- 
pendent galleries. 

Craters not occupied. It is well to see what goes on at the 
bottom. An outpost of several men or a sentinel may be posted 
for this purpose in a communicating trench on the friendly rim. 
Two communicating trenches may also be used to crown the 
friendly rim with a trench with slight counterslope. The out- 
posts place a dozen loopholes permitting fire on the bottom. We 
may also fill up the bottom with chevaux de frise and other 
auxiliary obstacles that can be thrown in. If the craters are 
in the way, we can always turn them by mining. (See figures 
for different examples : ) 


Ixample of Wine Croters 

t hrt line trench 
t Crater 

RppCom mvnicatinrf trench 

T Trench crowning rim on enemy jidc 

1C Wiretntanfement 

by the enemy 

C Mine Crater 

T I* line trench 

G* 6llery destroyed by I 
&<? Intact' galleriei allo 
t-f, Which fillvjienemy c 

to be placed 


/hint crater not to be occvfltd* 

t Jvmpinjf off trench 

T Trench crownind friendly rim 
UM.1 Loophole* overlooking the bottom and enemy rim 

Planking avtomatk-rlflt 

lYlre entanglement 

Create ne.leva<) w"l (Jltin for 
placing r-Kh.w Jvn> orthro.mj tamfc. 
.t M.nd M' which the prti tf 
tfy trench. 

Crater for f tanking p*rposet 

Fig H Pttroyin^ a rortior of emy trench by mtaro or rwo m(n crter>. 
6 >' Commvniustmj Gtrman trenches cvt off bjr 
5 5' Salient vnder'*hicji E.E ore exploded 

lnj machine (Jvm between 5*3'cwt off by rim of cra)r. 


A 000 550 1 53 1